title: Increased expression of a gene coding for NAD:glyceraldehyde-3-phosphate dehydrogenase during the transition from C3 photosynthesis to crassulacean acid metabolism in Mesembryanthemum crystallinum.
abstract: We utilized differential plaque hybridization to identify three cDNA clones for transcripts which increase in abundance during the salinity-induced transition from C3 photosynthesis to crassulacean acid metabolism (CAM) in Mesembryanthemum crystallinum. Although there are differences in the abundance of these transcripts in unstressed tissue, steady-state levels of all three increased within 30 h following irrigation with 0.5 M NaCl. One cDNA encodes the cytosolic form of glyceraldehyde-3-phosphate dehydrogenase (D-glyceraldehyde-3-phosphate:NAD+ oxidoreductase (phosphorylating) (NAD-GAPDH], an enzyme involved in the production of phosphoenolpyruvate for CO2 fixation at night and the conversion of pyruvate to storage carbohydrate during the day. Coding region and 3'-noncoding sequence probes were used to examine the expression of NAD-GAPDH transcripts in leaf and root tissue. We show that the gene encoding the NAD-GAPDH cDNA is expressed in both leaf and root tissue during C3 photosynthesis and CAM. NAD-GAPDH transcript levels increase rapidly in leaf (but not in root) tissue during the transition to CAM. Our data indicate that the predominant NAD-GAPDH transcript expressed during C3 photosynthesis and CAM is encoded by a single gene in M crystallinum. These results imply that the transition to CAM in some cases involves an upward readjustment in the level of a gene product expressed during C3 photosynthesis, rather than the expression of a CAM-specific isoform with unique regulatory or kinetic properties.
authors.affiliation: Department of Biochemistry, University of Arizona, Tucson 85721.
authors.forename: J A
authors.initials: JA
authors.lastname: Ostrem
authors.forename: D M
authors.initials: DM
authors.lastname: Vernon
authors.forename: H J
authors.initials: HJ
authors.lastname: Bohnert
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002264:Carboxylic Acids / Q000378:metabolism*; D003001:Cloning, Molecular; D015870:Gene Expression; D017343:Genes, Plant; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000235:genetics*; D015151:Immunoblotting; D007256:Information Systems; D007700:Kinetics; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D010788:Photosynthesis; D010944:Plants / Q000201:enzymology / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: D002264:Carboxylic Acids; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases